| 1. |
- Schmidt, P.T., et al.
(författare)
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Circulating ghrelin levels after food intake during different phases of the migrating motor complex in man.
- 2006
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Ingår i: European Journal of Clinical Investigation. - : Wiley. - 0014-2972 .- 1365-2362. ; 36:7, s. 503-509
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Tidskriftsartikel (refereegranskat)abstract
- Background The timing of the migrating motor complexes (MMC) at food intake may influence gastric emptying and release of regulatory hormones. This report studies the relationships between phases I (motor quiescence) and II (intermediate frequency contractions) of MMC and prandial gut hormone response. Materials and methods Seven fasting volunteers ingested a meal during phase I or II of MMC verified by manometry, using paracetamol as a marker for gastric emptying. Blood was sampled before, during and 210 min after food intake for analysis of ghrelin, motilin, insulin and paracetamol. Results The basal level of ghrelin during phase I was 127·5 ± 25·4 pmol L-1 and during phase II was 132·4 ± 24·8 pmol L-1. After food intake during phase I, ghrelin fell to 77·2 ± 10 pmol L-1; in phase II it fell to 82·7 ± 17·8 pmol L-1 within 60 min and returned to baseline levels after 120 min. Baseline levels of motilin were 16 ± 2 pmol L-1 and 18 ± 3 pmol L-1 during phases I and II, respectively. After food, motilin decreased to 8·5 ± 0·7 pmol L-1 and 8·7 ± 1·0 pmol L-1 within 60 min and returned to baseline after 90 min. Insulin levels in phases I and II were 8·1 ± 1·2 mU L-1 and 8·6 ± 0·7 mU L-1, respectively, reaching 138·9 ± 35·6 mU L-1 and 167·4 ± 30·0 mU L-1 at 45 min postprandially. Conclusions The nutritional status of the gastrointestinal tract at food intake had only a limited impact on plasma ghrelin. After food intake, plasma ghrelin drops, similar to motilin, and resumes preprandial levels within 120 min.
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| 2. |
- Kristensson, E, et al.
(författare)
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Acute psychological stress raises plasma ghrelin in the rat.
- 2006
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Ingår i: Regulatory Peptides. - : Elsevier BV. - 0167-0115 .- 1873-1686. ; 134:2-3, s. 114-117
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Tidskriftsartikel (refereegranskat)abstract
- Ghrelin is produced by the A-like cells of the stomach and mobilized by food deprivation. It was reported recently that acute psychological stress increases ghrelin gene expression in rat oxyntic mucosa. The aim of this study was to examine the effect of such stress on circulating ghrelin levels. To this end, we measured plasma ghrelin in Wistar Kyoto (WKY) rats (a high-anxiety strain) and Sprague–Dawley (SPD) rats (a low-anxiety strain), exposed to water avoidance stress for 60 min. Blood was collected before and after the stress. Acute stress increased the plasma ACTH concentration not, vert, similar5-fold (p < 0.01) in both strains of rats, while plasma ghrelin increased by 85% (p < 0.01) in the SPD rats and by 40% (p < 0.001) in the WKY rats. Ghrelin levels after acute stress were higher (p < 0.05) in the SPD rats than in the WKY rats. Sham stress did not affect plasma ghrelin. We conclude that acute psychological stress mobilizes ghrelin and that the SPD rats respond with a higher plasma ghrelin concentration than the WKY rats.
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| 3. |
- Aleksandrovskii, A.N., et al.
(författare)
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On the polyamorphism of fullerite-based orientational glasses.
- 2005
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 31:5, s. 429-444
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Tidskriftsartikel (refereegranskat)abstract
- The dilatometric investigation in the temperature range of 2–28 K shows that a first-orderpolyamorphous transition occurs in the orientational glasses based on C60 doped with H2, D2 andXe. A polyamorphous transition was also detected in C60 doped with Kr and He. It is observed thatthe hysteresis of thermal expansion caused by the polyamorphous transition (and, hence, the transitiontemperature) is essentially dependent on the type of doping gas. Both positive and negativecontributions to the thermal expansion were observed in the low-temperature phase of the glasses.The relaxation time of the negative contribution occurs to be much longer than that of the positivecontribution. The positive contribution is found to be due to phonon and libron modes, whilst thenegative contribution is attributed to tunneling states of the C60 molecules. The characteristictime of the phase transformation from the low-T phase to the high-T phase has been found for theC60–H2 system at 12 K. A theoretical model is proposed to interpret these observed phenomena.The theoretical model proposed, includes a consideration of the nature of polyamorphism inglasses, as well as the thermodynamics and kinetics of the transition. A model of noninteractingtunneling states is used to explain the negative contribution to the thermal expansion. The experimentaldata obtained is considered within the framework of the theoretical model. From the theoreticalmodel the order of magnitude of the polyamorphous transition temperature has been estimated.It is found that the late stage of the polyamorphous transformation is described well by theKolmogorov law with an exponent of n = 1. At this stage of the transformation, the two-dimensionalphase boundary moves along the normal, and the nucleation is not important.
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| 4. |
- Cato, Ingemar, et al.
(författare)
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DIOXINS AND OTHER POPS IN THE BALTIC SEA – TRENDS AND CURRENT
- 2009
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Ingår i: 29th International Symposium on Halogenated Persistent Organic Pollutants (Dioxin 2009) in Bejing, China, August 25-30, 2009.
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Konferensbidrag (refereegranskat)abstract
- This paper summarizes a project that was initiated by the Swedish Environmental Protection Agency (EPA) in 2006. It involved several field studies and fate model calculations with the aim to better understand the present contamination situation of dioxins and other persistent organic pollutants (POPs) in the Baltic Sea region. Atmospheric inputs were found to be the dominant external source for all of the selected POPs (dioxins, PCBs and HCB). The model also predicted a significant decline of POP-levels in Baltic surface water if atmospheric concentrations are reduced. This issue is highly prioritized by the Swedish EPA since TEQ-levels of fatty fish exceed maximum residue limits set by the EU. Dioxin source regions were identified by air measurements and analysis of air mass origin. It was found that air that had passed over the European continent contained the highest concentrations, and the congener composition indicated that several major sources types may exist. This research has high relevance for the Swedish EPA, and continued efforts for resolving the dioxin issue of the Baltic Sea will follow.
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| 5. |
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| 6. |
- Dolbin, Alexander V., et al.
(författare)
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Specific features of thermal expansion and polyamorphism in CH4 – C60 solutions at low temperatures
- 2007
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 33:12, s. 1068-1072
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Tidskriftsartikel (refereegranskat)abstract
- The temperature dependence of the linear thermal expansion coefficient alpha(T) is investigated in the temperature range of 2.5 to 23 K for two different CH4-C-60 solutions in which CH4 molecules occupy 24 and 50% of the octahedral interstitial sites of the C-60 lattice. In both cases, alpha(T) exhibits hysteresis, suggesting the existence of two types of orientational glass associated with these solutions. The temperature of the first-order phase transition between these two glasses is estimated, and the behavior of these two glasses is compared. The characteristic times of thermalization tau(1), reorientation of the C-60 molecules tau(2), and of the phase transformation between the glasses tau('), are estimated for these solutions. Both the temperature dependence of alpha(T) and the characteristic thermalization time tau(1) are found to have features near the phase transition temperature, and an explanation is put forward to explain these observed features.
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| 7. |
- Dolbin, Alexander V., et al.
(författare)
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The effect of the noncentral impurity-matrix interaction upon the thermal expansion and polyamorphism of solid CO-C60 solutions at low temperatures
- 2008
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Ingår i: Fizika Nizkikh Temperatur. - : AIP Publishing. - 0132-6414. ; 34:6, s. 592-598
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Tidskriftsartikel (refereegranskat)abstract
- Orientational glasses with CO molecules occupying 26 and 90% of the octahedral interstitial sites in the C60 lattice have been investigated by the dilatometric method in a temperature interval of 2.5–22 K. At temperatures 4–6 K the glasses undergo a first-order phase transition which is evident from the hysteresis of the thermal expansion and the maxima in the temperature dependences of the linear thermal expansion coefficients a(T), and the thermalization times t1(T) of the samples. The effect of the noncentral CO–C60 interaction upon the thermal expansion and the phase transition in these glasses was clarified by comparing the behavior of the properties of the CO–C60 and N2–C60 solutions.
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| 8. |
- Dolbin, Alexander V., et al.
(författare)
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Thermal expansion of solutions of deuteromethane in fullerite C60 at low temperature : Isotopic effect
- 2009
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics. - 1063-777X .- 1090-6517. ; 35:3, s. 226-231
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Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion of CD4 solutions in the orientational glass C60 with molar concentration of deuteromethane 20 and 50% has been investigated in the temperature range 2.5–23 K. The orientational glass CD4–C60 undergoes a first-order phase transition in the temperature interval 4.5–55 K. This transition is manifested as hysteresis of the linear thermal expansion coefficient alpha as well as maxima in the temperature dependences alpha(T) and tau1(T), where tau1 is the characteristic thermalization time of the experimental samples. The characteristic re-orientation times of the C60 molecules and the characteristic phase transformations occurring in the experimental solutions are determined. The results of the present study are compared with the results of a similar study of the solution CH4–C60. It is concluded that tunneling rotation of the CH4 and CD4 molecules occupying interstitial positions in the fullerite C60 lattice occurs.
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| 9. |
- Fomenko, L.S., et al.
(författare)
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Low temperature microhardness of Xe-intercalated fullerite C60
- 2005
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 31:5, s. 454-458
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Tidskriftsartikel (refereegranskat)abstract
- The Vickers microhardness of Xe-intercalated polycrystalline fullerite C60 (XexC60, x~=0.35) is measured in a moderately low temperature range of 77 to 300 K. A high increase in the microhardness of the material (by a factor of 2 to 3) as compared to that of pure C60 single crystals is observed. It is shown that the step-like anomaly in the temperature dependences of the microhardness of pure C60 single crystals recorded under the orientational fcc-sc phase transition (Tc~=260 K) is also qualitatively retained for XexC60, but its onset is shifted by 40 K towards lower temperatures and the step becomes less distinct and more smeared. This behavior of H-barV(T) correlates with x-ray diffraction data, the analysis of which revealed a considerable influence of xenon interstitial atoms on the peculiar features of fullerite thermal expansion due to orientational phase transitions (see the paper by A.I. Prokhvatilov et al. in this issue).
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| 10. |
- Galtsov, N. N., et al.
(författare)
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Intercalation of fullerite C60 with N2 molecules : an investigation by X-ray powder diffraction
- 2007
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics (AIP). - 1063-777X .- 1090-6517. ; 33:10, s. 881-885
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Tidskriftsartikel (refereegranskat)abstract
- The lattice parameter a of fullerite C60 intercalated with N2 molecules is investigated in the temperature interval 6–295K by x-ray diffraction. It is found that the interstitial molecular N2 has a considerable effect on both the orientational phase transition temperature Tc and the orientational glass formation temperature Tg. Hysteresis of a(T) in the Tc and Tg regions is detected, along with an abrupt change in volume over the region defining Tc. Complete intercalation of C60 with N2 molecules results in a 0.2% increase in the lattice parameter, which persists over the whole temperature range. Evidence is also obtained that the interstitial guest molecular N2 induces a slight deformation of the cubic symmetry of the C60 host lattice.
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